Risk factors for disease associated with influenza virus infections during three epidemics in horses

OBJECTIVE: To identify risk factors associated with respiratory tract disease in horses during 3 epidemics caused by influenza virus infections. DESIGN: Cross-sectional and prospective longitudinal observational studies. ANIMALS: 1,163 horses stabled at a Thoroughbred racetrack. PROCEDURES: Investigations were conducted during a 3-year period. An epidemic of respiratory tract disease caused by influenza virus infections was identified in each year. Routine observations and physical examinations were used to classify horses' disease status. Data were analyzed to identify factors associated with development of disease. RESULTS: Results were quite similar among the epidemics. Concentrations of serum antibodies against influenza virus and age were strongly associated with risk of disease; young horses and those with low antibody concentrations had the highest risk of disease. Calculation of population attributable fractions suggested that respiratory tract disease would have been prevented in 25% of affected horses of all horses had high serum antibody concentrations prior to exposure. However, recent history of vaccination was not associated with reduction in disease risk. Exercise ponies had greater risk of disease than racehorses, which was likely attributable to frequent horse-to-horse contact. CONCLUSIONS AND CLINICAL RELEVANCE: Particular attention should be paid to young horses, those with low serum antibody concentrations, and horses that have frequent contact with other horses when designing and implementing control programs for respiratory tract disease caused by influenza virus infections. It appears that control programs should not rely on the efficacy of commercial vaccines to substantially reduce the risk of disease caused by influenza virus infections.     

The association between serological titers in infectious bovine rhinotracheitis virus, bovine virus diarrhea virus, parainfluenza-3 virus, respiratory syncytial virus and treatment for respiratory disease in Ontario feedlot calves.

A seroepidemiological study of the association between antibody titers to infectious bovine rhinotracheitis, parainfluenza-3, bovine virus diarrhea and bovine respiratory syncytial viruses, and treatment for bovine respiratory disease was conducted. A total of 322 calves from five different groups were bled on arrival, then one month later all cases (cattle treated for bovine respiratory disease) were rebled together with an equal number of controls (cattle not treated for any disease). Titers to these viruses varied significantly from group to group. Based on seroconversion, infectious bovine rhinotracheitis virus was active in 4.4%, bovine virus diarrhea virus in 24%, parainfluenza-3 virus in 69.5% and bovine respiratory syncytial virus in 71.3% of the cattle. Cattle with low titers to infectious bovine rhinotracheitis and/or bovine respiratory syncytial viruses on arrival, were at increased risk of subsequent treatment for bovine respiratory disease. Treated cattle also had significantly greater increases to parainfluenza-3 and/or bovine virus diarrhea viruses than control calves. Treatment rates varied considerably from group to group and were not strongly correlated with weight gain in the postarrival period.     

几例犊牛肺炎的诊疗体会

犊牛肺炎是犊牛的一种常见病,以小叶性肺炎多见,多发于气温低、天气严寒的1-3月份出生的6~30日龄的犊牛。通过病因调查分析,该病可能发生的原因是阴天、雨天、风天和夜间低温、牛舍空气污浊、有烟雾、牛只拥挤、缺乏运动等。临床检查发现主要是呼吸道症状。患肺炎的犊牛,死亡率很高,患过肺炎的犊牛很容易发生呼吸道疾病。通过以抗菌素、磺胺类为主,配以强心补液的治疗措施获得良好疗效。因此笔者认为,应采用正确的饲养管理预防,并及时给予治疗病牛,才能避免造成更大经济损失。     

Evaluation of the ability of orally administered aspirin to mitigate effects of 3-methylindole in feedlot cattle

OBJECTIVE: To evaluate the ability of orally administered aspirin to mitigate 3-methylindole (3MI)-induced respiratory tract disease and reduced rate of gain in feedlot cattle. ANIMALS: 244 beef cattle. PROCEDURE: In a masked, randomized, controlled field trial, calves were untreated (controls) or received a single orally administered dose of aspirin (31.2 g) on entry into a feedlot. Serum 3MI concentrations were measured on days 0, 3, and 6. Rumen 3MI concentration was measured on day 3. Cattle were observed daily for clinical signs of respiratory tract disease. Lungs were evaluated at slaughter for gross pulmonary lesions. RESULTS: Mean daily gain (MDG) in cattle treated with aspirin, compared with control cattle, was 0.06 kg greater in the backgrounding unit and 0.03 kg greater for the overall feeding period. Neither serum nor rumen 3MI concentrations appeared to modify this effect. Cattle treated with aspirin were more likely to be treated for respiratory tract disease. Mortality rate, gross pulmonary lesions, and serum and rumen 3MI concentrations were similar between groups. Increased rumen 3MI concentration was associated with a small difference in risk of lung fibrosis. CONCLUSIONS AND CLINICAL RELEVANCE: Cattle given a single orally administered dose of aspirin on feedlot entry had higher MDG in the backgrounding unit and for the overall feeding period, but this finding could not be attributed to mitigation of effects of 3MI. This may have been influenced by low peak 3MI production and slow rates of gain.     

Risk factors for epidemic respiratory disease in Norwegian cattle herds

An epidemic of acute respiratory disease associated with bovine respiratory syncytial virus (BRSV) occurred during the winter and spring of 1995 in two neighbouring veterinary districts in the south-eastern part of Norway.The objective of this study was to describe the time course of the outbreak associated with BRSV in the cattle herds, and to determine the association between selected herd factors and the risk of experiencing a herd outbreak of acute respiratory disease.Data from 431 cattle herds on the dates of disease occurrence, location of the farms, herd size, age profile and production type were collected retrospectively for 1995. The risk of acute respiratory disease occurring in a cattle herd was related to the herd size as well as the type of production, with an expressed interaction between these two variables. From the Cox proportional-hazards model, the risk of a herd outbreak in a mixed herd of 20 animals was estimated to be 1.7-times greater than in a dairy herd and 3.3-times greater than a beef herd (reference category) of a comparable size. On increasing the herd size to 50 animals, the risk increased 1.3-fold for a mixed herd, 3.3-fold for a dairy herd, and 2.1-fold for a beef herd, compared to the risk for a corresponding type of herd of 20 animals.     

Serological evidence of Mycoplasma cynos infection in canine infectious respiratory disease

A high proportion of dogs suffer from respiratory disease when they are placed in kennels for vacation or re-homing. The role of Mycoplasma cynos as an initiating agent in canine infectious respiratory disease was investigated by examining the serological response of dogs to this organism at the time of entry into a large re-homing kennel. Forty-two paired serum samples from dogs (21-day interval) were examined for antibody to M. cynos using Western blotting. The development of antibody in the serum was related to clinical disease recorded over the same period. Sixty seven per cent of the dogs showed a two-fold or greater rise in antibody to M. cynos during the first 3 weeks in the kennel. Reactivity with a 45 kDa antigen was dominant. Of those showing a positive serological reaction, 80% had recorded clinical respiratory disease while 20% remained healthy. The findings of this study show that an antibody response to M. cynos is common in dogs entering the re-homing kennel and is positively related to the development of clinical respiratory disease.     

Ancillary testing for the ruminant respiratory system.

With greater use of a wide variety of diagnostic tools, such as transtracheal washing, respiratory endoscopy, chest radiography, thoracic ultrasonography, blood gas analysis, and lung biopsy, veterinarians are gaining tremendous insight into pathogenic mechanisms of the ruminant respiratory system. We have available many diagnostic aids; some fairly simple and inexpensive, others highly sophisticated and presently at far greater cost than justifiable on most individual food animals. Some methods recently developed, such as same-day viral particle detection in BAL samples,6 have tremendous potential for rapid and accurate diagnosis in ruminant pulmonary medicine. Undoubtedly, future research in this area will provide an ever widening array of powerful and rapid diagnostic aids to deal with respiratory disease of ruminants.     

Use of tilmicosin in a severe outbreak of respiratory disease in weaned beef calves

Severe respiratory disease, associated with seroconversion to bovine respiratory syncitial virus (BRSV), caused the death of two cattle and necessitated antibiotic treatment of 70 calves (rectal temperature of 39.6°C or greater) from a group of 96 (73%) during an 8-day period. Tilmicosin injection resulted in a reduction in median rectal temperature from 40.3°C to 39.2°C and 39.0°C for the first and second days after treatment. The rectal temperature was 39.5°C or lower in 72% (48 of 67) and 96% (64 of 67) of cattle 1 and 2 days after tilmicosin treatment, respectively. Ten cattle were re-treated with tilmicosin 6 to 16 days after the first treatment. Our study demonstrated that bovine respiratory syncytial virus infection could cause severe respiratory disease in a beef herd that had no previous history of BRSV-related disease. Secondary bacterial invasion after BRSV infection was controlled effectively by tilmicosin treatment but repeat antibiotic treatments were occasionally necessary due to bacterial re-infection of the respiratory tract.     

Small animal bronchoscopy.

Bronchoscopy is a useful diagnostic and therapeutic tool in veterinary medicine. The increased availability of fiberoptic technology and video-endoscopy has enhanced recognition of the benefits gained from visualization of the lower airways in animals with lower respiratory tract disease. Specimens retrieved from the lower airway during bronchoscopy have greater diagnostic capacity, and a better understanding of the pathophysiology of disease is provided through application of bronchoscopy to animals with respiratory tract disease.     

A study of feline upper respiratory tract disease with reference to prevalence and risk factors for infection with feline calicivirus and feline herpesvirus.

A cross-sectional survey of a convenience sample of cats was carried out to determine the prevalence of and risk factors for respiratory tract disease, feline calicivirus (FCV) infection and feline herpesvirus (FHV) infection. Seven hundred and forty cats were studied; samples for isolation of FCV and FHV were obtained from 622 (84%). Data on individual cat and household variables were obtained by questionnaire for each cat and analysed using univariable and logistic regression analysis. Thirty-eight percent (282/740) of cats surveyed had respiratory tract disease. Eighteen of 24 predictor variables were found to be significantly (P<0.05) associated with the presence of respiratory tract disease in a cat on univariable analysis. Following logistic regression, several factors retained significance including isolation of FCV and FHV, younger cats (4-11 months of age) and multiple cat households. A negative association was found with breeding catteries and other types of household in comparison with rescue catteries. Overall, feline calicivirus was isolated from 162/622 (26%) of cats sampled; 33% of the cats with respiratory tract disease were FCV positive compared to 21% of healthy cats. Variables significantly associated with FCV isolation on logistic regression were the presence of respiratory tract disease and contact with dogs with and without respiratory tract disease. Feline herpesvirus was isolated from 30/622 (5%) of all cats sampled; 11% of cats with respiratory tract disease were FHV positive compared to 1% of healthy cats. Variables significantly associated with FHV isolation on univariable analysis included age, gender, and the presence of respiratory tract disease. Vaccination showed a negative association. Logistic regression analysis of the data for FHV was limited by the sample size and the low prevalence of FHV.     

The effect of isoprinosine and levamisole on factors relevant to protection of calves against respiratory disease

Experiments to characterize the effects of two immunomodulators, namely, isoprinosine and levamisole, on factors relevant to the resistance of calves to respiratory infection were undertaken. Daily oral doses of isoprinosine decreased the influx of neutrophils into the respiratory tract, increased membrane immunoglobulin and complement receptor expression on cells from bronchoalveolar lavage samples and decreased the severity of respiratory disease. Additional intravenous doses produced similar effects on neutrophil migration to the respiratory tract and on membrane receptor expression, but the changes were no greater than those seen with oral isoprinosine alone. No significant changes in the anti-bacterial activity of cells in bronchoalveolar lavage samples followed isoprinosine treatment. In vitro incubation of pulmonary alveolar macrophages harvested from normal calves with isoprinosine increased their expression of immunoglobulin and complement receptors. Levamisole did not affect neutrophil migration to the lower respiratory tract or membrane receptor expression by pulmonary alveolar macrophages after in vivo or in vitro treatment. The immunomodulatory effects of isoprinosine beneficially increase the resistance of calves to respiratory disease, and are potentially useful in the control of infectious diseases of farm animals.     

Comparison of Serum Amyloid A in Horses With Infectious and Noninfectious Respiratory Diseases

The acute phase protein serum amyloid A (SAA) has been shown to be a useful inflammatory parameter in the horse, but studies showing SAA responses to specific respiratory disease etiologies are limited. The goal of this study was to evaluate SAA responses in horses with infectious and noninfectious respiratory diseases as well as healthy, control horses. Two hundred seven horses were grouped into the following categories: equine influenza virus (EIV), equine herpesvirus-4 (EHV-4), Streptococcus equi subspecies equi (S. equi ss equi), inflammatory airway disease (IAD), and healthy controls. Serum amyloid A concentrations were determined for all horses on serum using a stall-side lateral flow immunoassay test. Serum amyloid A levels were found to be significantly greater for infectious respiratory diseases (EIV, EHV-4, S. equi ss equi) and horses with IAD when compared to control horses. There was a significant difference between viral and bacterial infections and IAD. Although SAA values from horses with S. equi ss equi were significantly greater when compared to horses with viral infections (EIV/EHV-4), the wide range of SAA values precluded accurate classification of the infectious cases. In conclusion, SAA is more reliably elevated with infections of the respiratory tract rather than noninfectious airway conditions. This can facilitate early detection of respiratory infections, help track disease progression, and aid practitioners in making recommendations about proper biosecurity and isolation of potentially contagious horses.     

Polymicrobial respiratory disease in pigs

Respiratory disease in pigs is common in modern pork production worldwide and is often referred to as porcine respiratory disease complex (PRDC). PRDC is polymicrobial in nature, and results from infection with various combinations of primary and secondary respiratory pathogens. As a true multifactorial disease, environmental conditions, population size, management strategies and pig-specific factors such as age and genetics also play critical roles in the outcome of PRDC. While non-infectious factors are important in the initiation and outcome of cases of PRDC, the focus of this review is on infectious factors only. There are a variety of viral and bacterial pathogens commonly associated with PRDC including porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus (SIV), porcine circovirus type 2 (PCV2), Mycoplasma hyopneumoniae (MHYO) and Pasteurella multocida (PMULT). The pathogenesis of viral respiratory disease is typically associated with destruction of the mucocilliary apparatus and with interference and decrease of the function of pulmonary alveolar and intravascular macrophages. Bacterial pathogens often contribute to PRDC by activation of inflammation via enhanced cytokine responses. With recent advancements in pathogen detection methods, the importance of polymicrobial disease has become more evident, and identification of interactions of pathogens and their mechanisms of disease potentiation has become a topic of great interest. For example, combined infection of pigs with typically low pathogenic organisms like PCV2 and MHYO results in severe respiratory disease. Although the body of knowledge has advanced substantially in the last 15 years, much more needs to be learned about the pathogenesis and best practices for control of swine respiratory disease outbreaks caused by concurrent infection of two or more pathogens. This review discusses the latest findings on polymicrobial respiratory disease in pigs.     

Equine Viral Respiratory Pathogen Surveillance at Horse Shows and Sales

Equine respiratory viral infections cause significant worldwide disease and economic loss. Common causes include equine influenza virus (EIV) and equine herpesviruses-1 and -4 (EHV-1 and -4), and risk of exposure to these agents may be highest in young horses commingling at sales and competitive events. A surveillance study was conducted at two horse shows and two Thoroughbred sales to determine whether horses shed EHV-1, EHV-4, or EIV on arrival, or 2-4 days later, and whether shedding was associated with identifiable risk factors. Real-time polymerase chain reaction assays were used to detect EHV-1, EHV-4, and EIV nucleic acid in nasal swabs obtained from 369 horses at the four events. In response to evidence of clinical disease, 82 additional horses were sampled at two farms providing horses for one of the sales. On arrival at the events, shedding of EHV-1 was detected in 3.3%, EHV-4 in 1.1%, and EIV in 0.8% of horses. EHV-1 was detected at low levels, and EHV-1 and EHV-4 detection was not associated with clinical disease. EIV was detected only in horses at a Thoroughbred sale, in association with an outbreak of respiratory disease traced back to regional farms. On arrival at events, horses younger than 2 years had a significantly greater risk of shedding EHV-1 compared with older horses; no other significant risk factors associated with viral shedding were identified. Thus, there is a risk of exposure to EIV, EHV-1, and EHV-4 at equine events, and horses and events should be managed to mitigate this risk.     

Clinical signs, diagnosis, and treatment of alkalemia in dogs: 20 cases (1982-1984)

Alkalemia (pH greater than 7.50) was measured in 20 dogs admitted over a 3-year period for various clinical disorders. Alkalemia was detected in only 2.08% of all dogs in which blood pH and blood-gas estimations were made. Thirteen dogs had metabolic alkalosis (HCO3- greater than 24 mEq/L, PCO2 greater than 30 mm of Hg), of which 8 had uncompensated metabolic alkalosis, and of which 5 had partially compensated metabolic alkalosis. Seven dogs had respiratory alkalosis (PCO2 less than 30 mm of Hg, HCO3- less than 24 mEq/L); 4 of these had uncompensated respiratory alkalosis and 3 had partially compensated respiratory alkalosis. Ten dogs had double or triple acid-base abnormalities. Dogs with metabolic alkalosis had a preponderance of clinical signs associated with gastrointestinal disorders (10 dogs). Overzealous administration of sodium bicarbonate or diuretics, in addition to anorexia, polyuria, or hyperbilirubinemia may have contributed to metabolic alkalosis in 8 of the dogs. Most of the dogs in this group had low serum K+ and Cl- values. Two dogs with metabolic alkalosis had PCO2 values greater than 60 mm of Hg, and 1 of these had arterial hypoxemia (PaO2 less than 80 mm of Hg). Treatments included replacement of fluid and electrolytes (Na+, K+, and Cl-), and surgery as indicated (8 dogs). Six dogs with respiratory alkalosis had a variety of airway, pulmonary, or cardiac disorders, and 3 of these had arterial hypoxemia. Two other dogs were excessively ventilated during surgery, and 1 dog had apparent postoperative pain that may have contributed to the respiratory alkalosis.(ABSTRACT TRUNCATED AT 250 WORDS)     

The frequency, distribution and effects of antibodies, to seven putative respiratory pathogens, on respiratory disease and weight gain in feedlot calves in Ontario.

During 1983-85, 279 calves requiring treatment for bovine respiratory disease and 290 comparison (control) animals from 15 different groups of feedlot calves were bled on arrival and again at 28 days postarrival. Their sera were then analyzed for antibodies to seven putative respiratory pathogens. On arrival, the prevalences of indirect agglutination titers to Pasteurella haemolytica, P. haemolytica cytotoxin, Mycoplasma bovis and M. dispar were greater than 50%, the prevalence of titers to bovine virus diarrhea virus (BVDV) was approximately 40%, and the prevalences of titers to infectious bovine rhinotracheitis virus (IBRV), bovine respiratory syncytial virus (RSV) and parainfluenza virus type 3 (PIV3) were all below 25%. Seroconversion during the first month after arrival occurred in more than half the calves to P. haemolytica cytotoxin, PIV3 and RSV. Seroconversion of agglutination titers to P. haemolytica, Mycoplasma and BVDV occurred in about 40% of calves, and seroconversion to IBRV was infrequent (less than 5%). Initial titers were negatively correlated to subsequent titer changes within organism. Initial titers, and titer changes between organisms were essentially independent. Light calves had an increased risk of being selected for treatment for respiratory disease. Seroconversion to P. haemolytica cytotoxin, RSV and BVDV were predictive of respiratory disease cases, explaining approximately 69% of all respiratory disease cases in the feedlots. It was not possible to accurately predict weight gain or relapse from the serological data.     

不同温度下AOX和COX途径对苜蓿种子萌发和幼根生长的影响

为了研究不同温度下交替氧化酶(Alternative oxidase,AOX)和细胞色素氧化酶(Cytochrome oxidase,COX)呼吸途径在紫花苜蓿(Medicago sativa L.)种子萌发过程中的作用,本研究以'新牧4号'和'甘农5号'紫花苜蓿为试验材料,采用呼吸电子传递链专一性抑制剂水杨基氧肟酸(...     

Factors affecting the development of respiratory disease complex in chickens

Factors playing a part in the development of respiratory disease complex in chickens were investigated in a series of experiments. The experimental infection was produced by exposing chickens to Mycoplasma gallisepticum and the B1 vaccine strain of Newcastle disease virus and later exposing them to aerosols containing the O1:K1 serotype of Escherichia coli. Chickens became susceptible (pericarditis or death) to E. coli 8 days after mixed respiratory disease challenge. One day after respiratory disease challenge, lesions consisted of edema and infiltration with lymphoid cells and heterophils. At the time of susceptibility to E. coli, the lesions were strongly lymphoid with many dense follicular areas and very few heterophils. The incidence of pericarditis and death was similar when the concentration of bacteria in the aerosol inoculum ranged between 10(9)/ml and 10(5)/ml. At the time of maximum susceptibility to aerosol challenge, chickens were less susceptible to intravenously administered E. coli than were the uninfected controls. Resistance of chickens that had been selectively bred for a high (HA) or low (LA) antibody response to sheep erythrocytes was compared. HA chickens were more resistant to respiratory agents and less resistant to E. coli than LA line chickens. When the lines were exposed to respiratory disease followed by exposure to aerosols containing E. coli, the HA line had the lowest incidence of pericarditis and death.     

野马追克喘散治疗猪呼吸道疾病效果试验

目的：应用野马追克喘散新兽药对呼吸道综合征进行临床疗效试验,为推广野马追克喘散提供科学依据。方法：将自然感染、症状典型、猪呼吸道综合征的140头病猪（杜长大三元杂交）,平均体重20～25kg,随机分为7个组,每组20头,其中第Ⅰ、Ⅱ、Ⅲ组用野马追克喘散治疗,分别以高、中、低剂量给药;第Ⅳ、Ⅴ组分别用麻杏石甘散、金花平喘散以常规剂量给药;Ⅵ、Ⅶ组以硫酸卡那霉素注射液（0.2mL/kg体重）和泰乐菌素（0.4mL/kg体重）以常规剂量给药。结果：野马追克喘散的治疗效果较麻杏石甘散和金花平喘散治疗效果好,治愈率也达93.3%。结论：野马追克喘散治疗猪气喘咳嗽疗效较高,收效较快,维持时间较长,是较理想的药物。     

Prevalence and specificity of antibodies to bovine respiratory syncytial virus in sera from feedlot and range cattle

The specificity of serum antibodies for the polypeptides of bovine respiratory syncytial virus (BRSV) was examined, using sera obtained from feedlot and range cattle. Test results in sera from feedlot cattle indicated a 60% rate of seroconversion and 95% seropositivity to BRSV, associated with lack of clinical signs indicative of respiratory tract disease. Exposure to other common respiratory tract viruses also was high (greater than or equal to 92% to bovine herpesvirus type 1, bovine viral diarrhea virus, and para-influenza virus type 3). Test results in sera from range cattle indicated BRSV seropositive rates of 28% in calves, 49% in yearling cattle, and 70% in mature cows; clinical signs of respiratory tract disease were not observed in these cattle. Antibodies to BRSV in sera from cattle in both environments reacted predominantly with polypeptides of molecular weight 80,000 through 85,000, 40,000, and 28,000. Reactivity to a glycoprotein of molecular weight between 43,000 and 44,000 and to several glycopolypeptides of smaller molecular weight increased in serum specimens obtained from feedlot cattle between time of entry into the feedlot and slaughter.